Generally, the widely-used peripheral input device of a computer system includes for example a mouse, a keyboard, a trackball, or the like. Via the keyboard, characters or symbols can be directly inputted into the computer system. As a consequence, most users and most manufacturers of input devices pay much attention to the development of keyboards. As known, a keyboard with scissors-type connecting elements is one of the widely-used keyboards.
FIG. 1 is a schematic perspective view illustrating the structure of a conventional notebook computer. As shown in FIG. 1, the conventional notebook computer 1 comprises a keyboard base 10, a top cover 11, a rotary shaft 12 and a keyboard 13. The top cover 11 comprises a display screen 111. The top cover 11 is rotatable through the rotary shaft 12. Consequently, the top cover 11 is closed to cover the keyboard base 10, or the top cover 11 is uplifted to allow the notebook computer 1 to be in a usage status. The keyboard 13 is installed on the keyboard base 10. When the keyboard 13 is operated by the user, a corresponding key signal is generated. Meanwhile, the notebook computer 1 is in a laptop mode.
The key structure of the keyboard 13 will be illustrated as follows. For succinctness, only one key structure is shown. FIG. 2 is a schematic side cross-sectional view illustrating a key structure of a conventional keyboard. As shown in FIG. 2, the conventional key structure 130 of the keyboard 13 comprises a keycap 1301, a scissors-type connecting element 1302, a rubbery elastomer 1303, a membrane switch circuit member 1304 and a base plate 1305. The keycap 1301, the scissors-type connecting element 1302, the rubbery elastomer 1303 and the membrane switch circuit member 1304 are supported by the base plate 1305. The scissors-type connecting element 1302 is used for connecting the base plate 1305 and the keycap 1301.
The scissors-type connecting element 1302 is arranged between the base plate 1305 and the keycap 1301, and the base plate 1305 and the keycap 1301 are connected with each other through the scissors-type connecting element 1302. The rubbery elastomer 1303 is enclosed by the scissors-type connecting element 1302. The membrane switch circuit member 1304 comprises plural key intersections (not shown). When one of the plural key intersections is triggered, a corresponding key signal is generated.
The rubbery elastomer 1303 is disposed on the membrane switch circuit member 1304. Each rubbery elastomer 1303 is aligned with a corresponding key intersection. When the rubbery elastomer 1303 is depressed, the rubbery elastomer 1303 is subjected to deformation to push the corresponding key intersection of the membrane switch circuit member 1304. Consequently, the corresponding key signal is generated.
The operations of the conventional key structure 130 in response to the depressing action of the user will be illustrated as follows. Please refer to FIG. 2 again. While the keycap 1301 is depressed, the keycap 1301 is moved downwardly to push the scissors-type connecting element 1302 in response to the depressing force. As the keycap 1301 is moved downwardly relative to the base plate 1305, the keycap 1301 pushes the corresponding rubbery elastomer 1303. At the same time, the rubbery elastomer 1303 is subjected to deformation to push the membrane switch circuit member 1304 and trigger the corresponding key intersection of the membrane switch circuit member 1304. Consequently, the membrane switch circuit member 1304 generates a corresponding key signal. When the keycap 1301 is no longer depressed by the user, no external force is applied to the keycap 1301 and the rubbery elastomer 1303 is no longer pushed by the keycap 1301. In response to the elasticity of the rubbery elastomer 1303, the rubbery elastomer 1303 is restored to its original shape to provide an upward elastic restoring force. In response to the elastic restoring force, the keycap 1301 is returned to its original position where it is not depressed.
Recently, a touch device is introduced into the market. The touch device is operated by using the user's finger directly or using a touch pen. Since the touch device is easy to use, many users and many manufacturers pay much attention to the touch device. For example, the display screen 111 of the notebook computer 1 is a touch screen with a touch control function. Moreover, a notebook computer having an inversely foldable screen is introduced into the market. FIG. 3 is a schematic perspective view illustrating a conventional notebook computer having an inversely foldable screen, in which the notebook computer is in a tablet mode. After the top cover 11 of the notebook computer 1 is rotated in the direction toward a rear side of the keyboard base 10 through the rotary shaft 12, the top cover 11 is folded to be contacted with a rear surface of the keyboard base 10 and the display screen 111 is exposed. Meanwhile, the notebook computer 1 has the outer appearance of a touch device such as a tablet computer. Since the display screen 111 is a touch screen, the notebook computer 1 can be used as a touch device.
However, the keyboard 13 of the notebook computer 1 in the tablet mode is also exposed. Consequently, when the notebook computer 1 is held by the user's hands, the fingers of the user may press the key structures 130. Since the pressed key structures 130 are moved downwardly to form a concave region, it is difficult for the user to stably hold the notebook computer 1. Moreover, if the key structure 130 is erroneously triggered when the notebook computer 1 is held by the user's hands, the notebook computer 1 also generates a key signal. Under this circumstance, the erroneous operation is generated. In other words, the conventional key structure for the notebook computer having an inversely foldable screen is not user-friendly.
Therefore, there is a need of providing a key structure capable of avoiding erroneous operations in response to the changed appearance.